<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <style>
        .box{
            width :100%;
            height: 800px;
  /* 图片地址 */    
        background-image: url(./kunkun.gif);
        /* 设置 2 个 宽和高 */
        background-size: 100% 100%;
        /* 位置 */
        background-position: center;
        /* 是否平铺 */
        background-repeat: no-repeat;   
        }
    </style>
    <title>Document</title>
</head>
<body>
    <div class="box"></div>
</body>
</html>